A computer host generally has a power supply device to filter wave, rectify current and transform voltage of an external electric power source (AC 110V or 220V power source), then out the electric power to various electronic devices (such as main board, hard disk, optical disk, etc.) of the host. As electric transformation will generate thermal energy, the power supply device or computer host usually is equipped with a radiation fan to disperse heat and lower the temperature. The electric power of the radiation fan also is supplied by the main power system of the power supply device. Thus when the host is power off, the power supply device stops connecting to the external power supply. The main power system also is OFF, and the radiation fan stops operation. However, the power supply device accumulates high temperature inside after operation and the temperature cannot drop immediately. This will cause damage of electronic elements after a prolonged period of time. Moreover, the non-stop power supply system still provides electric power to the main board and control switches to maintain required operations even after the main power system is shut down. These operations also generate heat. Due to the host usually is installed in a semi-closed environment, and the host location often is hidden and closed, the heat energy cannot be dispersed. This also affects other electronic elements.
The applicant has proposed a radiation fan power off deferring apparatus in U.S. Pat. No. 6,163,087 to remedy the aforesaid problems so that after the power supply of the host is shut down (REMODE OFF), the non-stop power supply system will supply electric power to the radiation fan to continue operation to disperse the heat of the host.